Systems have been described in which distance and the speeds are measured by radar (microwaves), especially short-range radar. Currently, radiator-surface antenna arrays (patch antennas) are used, among others, in which radiator surfaces (patches) are mounted directly on substrate materials or on top of foam materials. The radiator surfaces are excited either on the antenna side by feed lines or by coupling slots. The feed lines may be accommodated on an additional material, which is a different material in most cases, and the individual layers or coatings must be interconnected on top of each other. However, these antenna arrays have the disadvantage that the relative adjustment and the precise positioning of the individual material layers is highly complicated and difficult to implement.
Furthermore, antenna arrays have been manufactured according to a so-called triplate technology, in which electric connecting sections are arranged between two metallic coatings. Such antenna arrays are made up, for instance, of individual perforated metal plates, foils with antenna structures or feed lines and of foam intermediate layers. The individual layers are assembled by screw fitting, for example, and secured to prevent slippage. As a result of the fairly complicated design and the involved manufacturing process it requires, such antenna arrays are quite expensive.
Another type of antenna array is set up on a laminated printed-circuit board made up of an FR4 substrate, for example. A so-called softboard is laminated onto the printed circuit board, coupling slots being provided on one side of the softboard. A area is milled out from the FR4-substrate, foam material is inserted in this milled-out surface and the metal radiator surfaces, i.e., patches, are affixed thereon by means of a film, for example. This approach has the disadvantage of requiring a complicated manufacturing method, since holes must be milled out and foams inserted.
In addition, spurious radiation outside the useful frequency occurs in all known arrays, caused by processor pulses, radiation from components etc., for instance, and it is difficult to prevent it. Also, because of feed lines, for example, considerable portions of the useful electromagnetic radiation is radiated in undesired directions, such as in the direction of the vehicle frame or vehicle engine, and may have a detrimental effect on components installed in these areas.
Therefore, the underlying problem definition of the present invention, in general, is to provide an antenna array that has a compact design and reduces an electromagnetic radiation in unwanted directions.